The increased use of computers, mobile phones, electronic equipment and other short life high-tech devices creates a growing amount of waste typically containing ferrous metals, copper, aluminum, zinc, rare and precious metals. This situation poses the problem of recovering and processing of metals contained in the waste. Thus, such waste constitutes a veritable source of metals.
A known technique for recovery of metals is to load the waste (previously shredded to about 4 cm) in primary ovens or copper furnaces. This technique produces high emissions of dust, sulfur dioxide and gases containing halogens (chlorine and bromine). The gases thus require further complex processing. Another problem with this technique is that electronic waste generates a lot of heat during combustion of the plastic they contain. In other words, the high calorific value of electronic waste is an obstacle to this technique. The frequently high aluminum content in the treated waste is another problem, since the presence of aluminum in the slag or cinders increases their melting point so that treatment becomes very difficult. Because of these various drawbacks, primary oven capacity to handle electronic waste is limited.
Other recovery techniques use methods of fine shredding followed by magnetic and electrostatic separation to enrich and sort phases rich and poor in metals. For example, International application WO 2007/099204 describes a method comprising shredding the waste into particles of 2-4 mm, electrostatic charging of the materials by friction against a drum, followed by electron bombardment, and finally sorting of the materials using an electric field. However, such techniques are expensive (especially in view of the fine shredding that is necessary), only provide imperfect sorting and thus lead to poor performance of precious metal recovery.
In another approach, European patent EP 1,712,301 describes a method for processing electronic waste in which metal wire fragments are recovered from waste through a barrel provided with a textile strip to which the wire fragments adhere.
Attempts have also been eight to recover metals by fluidized bed pyrolysis. However, this technique has the disadvantage of mixing the metal with an additive (fluidizing medium) such as sand, quartz and the like, complicating recovery. Indeed, screening, which is carried out downstream from the pyrolysis, cannot effectively separate the additive from certain metallic dusts. Furthermore, such a method consumes more energy, a part of the metals gets oxidized and metals are entrained in the gas phase.
There is therefore a real need to develop a method for recovering the metals contained in electronic waste, which overcomes the disadvantages mentioned above. In particular, it is desirable to develop a simple the that consumes relatively little energy, does not require extensive treatment of the gases emitted, and makes it possible to obtain a good yield of recycled metals.